In continuous casting of steel, it often is necessary to change the grade of steel for the particular job without interrupting the continuous operation of the system. To this end, when the supply of one grade of molten metal to the mold of the continuous casting machine is completed, it is customary to immediately begin supplying the mold with the next grade of steel so that the casting operation proceeds on a continuous and uninterrupted basis. While a thin skin quickly forms on the outside of the molten metal as it passes through the mold, the interior of the casting remains liquid for a period of time during the casting and subsequent cooling operation. When the beginning of a new grade of molten steel joins the trailing end of the previous different grade steel in the mold an intermixing of the two grades of steel occurs, which can affect a segment of the casting 20 to 30 feet in length, which must be scrapped and ultimately reprocessed as secondary steel at considerable expense.
While proposals have been made for introducing a physical separator between the runs of different grades of steel in continuous casting machines, such efforts have been subject to further problems. When a steel plate or the like barrier is positioned into the mold immediately upon completion of the introduction of one grade of steel and prior to the introduction of the next, splattering of molten metal can occur when the subsequently introduced molten metal strikes the separating plate, which can contaminate the surrounding environment and create a safety hazard to personnel handling the separator plate. Moreover, it is difficult to position the separator plate in the mold between the grades of molten steel without leaving cavities or bubbles of gas entrapped about the separating plate, which can cause explosions and again dangerous splattering of the molten metal. Finally, manual manipulation of such steel separator plates, which are relatively heavy, can be fatiguing to workers, particularly in the hot environment adjacent the entrance to the mold.